1. Field of the Invention
The present invention relates to a TV, and more particularly, to a digital TV and a method of automatically switching a channel thereof.
2. Discussion of the Background Art
Generally, digital broadcasts transmit additional data along with video and audio data to provide viewers with a variety of services. However, the digital broadcasts differ in bandwidths for the respective areas and has limited bandwidths in use. Hence, in order to transmit both SD (standard definition) broadcasts and HD (high definition) broadcasts (having a data size several times greater than that of the SD broadcasting) within a limited bandwidth (ex., 7 MHz in Australia), the SD broadcasts having a data size as great as the data size of the HD broadcasts should be terminated in a time zone transmitting the HD broadcasts.
If several SD broadcasts are terminated while the HD broadcast is carried out, the corresponding SD broadcasting channels are at states having no signal carried thereon. Hence, in order to avoid providing viewers with a screen in a no-signal state, the TV channel is automatically switched to another channel. Specifically, a DVB (digital video broadcasting) system (a digital broadcasting standard used in Europe and Australia) uses a linkage descriptor including information for channel switch for automatic channel shifting.
The linkage descriptor is included in PSI (program specific information) of a transport stream (hereinafter abbreviated ‘TS’). A method of switching a broadcast program automatically using the linkage descriptor is explained by referring to FIG. 1 as follows.
Referring to FIG. 1, SD broadcasts (service_id=1070, 1071, 1072, and 1073) of four channels are carried out until a HD broadcast begins after 10 o'clock. Hence, three (service_id=1071, 1072, and 1073) of the SD broadcasts are terminated. Therefore, after 10 o'clock, one SD broadcast and one HD broadcast are carried out.
If the HD broadcast starts while a viewer watches the broadcast of the service ID of ‘1071’ (service_id=1071) during SD broadcasting, the channel watched by the viewer will become a no-signal channel, that is, failing to display a broadcast video.
In order to overcome such a problem, a control unit of a TV analyses a linkage descriptor of the PSI information of a transport stream, and switches the channel to a broadcast program designated by the linkage descriptor, i.e. the broadcast program (service_id=1070) to prevent the viewer from watching the no-signal channel.
The TV according to the background art ends the SD broadcast program watched by the viewer when the HD broadcasting begins, and then switches the channel to another channel automatically, whereby the viewer is through no fault of his own) due to the abrupt change of the channel.